The present disclosure relates, in general, to electronics, and more particularly, to electronic devices, apparatuses, systems, and methods for sensing a position, an angular position, or a linear position of a target.
Inductive position sensors are widely used in numerous industries and in a number of different applications. For example, in the automotive industry, inductive position sensors in vehicles can be used in to detect the position of the acceleration pedal, brake pedal, throttle, suspension, steering wheel, headlights, actuators, or any of various other components of the engine, transmission or vehicle. Similarly, inductive position sensors in a factory can be used to detect the position of levers, rotors, shafts, or other mechanical equipment. Conventional inductive position sensors typically include a single excitation coil, several receiver coils inductively coupled to the excitation coil, and a target coil or target element. The target element can be attached to a movable part, or can itself be a moveable part, for which it is desirable to know the position of The target element is designed to affect the inductive coupling between the excitation coil and the receiving coils as a function of its position. Circuitry is provided to compare the relative amplitudes between the several receiving coils.
A conventional inductive position sensor will now be described with reference to FIG. 1. Referring to FIG. 1, an inductive position sensor 100 is shown. The inductive position sensor 100 typically includes an AC source 102 coupled to a single excitation coil 104. The AC source 102 provides an alternating current to excitation coil 104 which in turn generates an electromagnetic field. Receiver coils 108 and 110 are configured such that the electromagnetic field generated by excitation coil 104 induces AC signals within receiver coils 108 and 110. A target element or coupler element 106 is placed within the electromagnetic field and is configured to affect the electromagnetic field as a function of its angular position θ. The configuration and position of target element 106 and receiver coils 108 and 110 is such that the AC signals induced in receiver coils 108 and 110 are different and such that both signals vary as a function of the angular position of target element 106. The angular position θ of target element 106 can be determined by relative amplitude measurement of the signal induced in receiver coil 108 compared to the signal induced in receiver coil 110. The relative amplitude measurement and determination of the angular position θ of target element 106 typically is performed by a signal processor 116.
The accuracy of position sensor 100 requires the amplitudes of signals to be measured precisely. Conventionally, however, the amplitudes of the signals induced within receiver coils 108 and 110 are small. For example, the amplitudes of the signals excited within receiver coils 108 and 110 can be hundredths or thousandths of the amplitude of excitation signal generated in excitation coil 104. A 5V excitation signal in excitation coil 104 could, for example, result in 10 mV signals, or smaller, being induced within receiver coils 108 and 110. In order to measure and compare the amplitudes of the two signals accurately, amplifiers 112 and 114 are used to amplify the two signals before processing them with signal processor 116. The use of two parallel channels having two separate amplifiers, however, introduces errors into the sensor system due to amplification mismatch. Conventional systems which use a single amplifier by time-division multiplexing both signals suffer from error introduced by a time mismatch and additionally suffer from slower processing speeds. Solutions to the both amplification mismatch and time mismatch have generally required complex circuitry increasing both the size and cost of the sensor. Accordingly, it is desirable to have an inductive position sensor which eliminates time and amplification mismatch. Additionally, it is also beneficial for the sensor to be small, cost effective and simple.
For simplicity and clarity of the illustration, elements in the figures are not necessarily to scale, are only schematic and are non-limiting, and the same reference numbers in different figures denote the same elements, unless stated otherwise. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. It will be appreciated by those skilled in the art that the words “during”, “while”, and “when” as used herein relating to circuit or system operation are not exact terms that mean an action takes place instantly upon an initiating action but that there may be some small but reasonable delay, such as a propagation delay, between the reaction that is initiated by the initial action. Additionally, the term “while” means that a certain action occurs at least within some portion of a duration of the initiating action. The use of the word “approximately” or “substantially” means that a value of an element has a parameter that is expected to be close to a stated value or position. However, as is well known in the art there may be minor variances that prevent the values or positions from being exactly as stated. It is well established in the art that variances of up to at least ten percent (10%) are reasonable variances from the ideal goal that may be described. When used in reference to a state of a signal, the term “asserted” means an active state of the signal and “inactive” means an inactive state of the signal. The actual voltage value or logic state (such as a “1” or a “0”) of the signal depends on whether positive or negative logic is used. Thus, “asserted” can be either a high voltage or a high logic or a low voltage or low logic depending on whether positive or negative logic is used and negated may be either a low voltage or low state or a high voltage or high logic depending on whether positive or negative logic is used. Herein, a positive logic convention is used, but those skilled in the art understand that a negative logic convention could also be used.
For simplicity and clarity of illustration, formulas and mathematical functions are used to represent signals and fields, however, one of ordinary skill in the art will understand that in practice, actual signals can differ, sometimes considerably, from their mathematical description due to component limitations, physical limitations, noise, errors, environmental influences, etc. Therefore, one of ordinary skill in the art will appreciate that the formulas and mathematical functions described herein are merely illustrative and are generally approximate. The terms “first”, “second”, “third” and the like in the Claims or/and in the Detailed Description of the Drawings, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments described herein are capable of operation in other sequences than described or illustrated herein.